Relationships between freshwater sedimentary diatoms and environmental variables in Subarctic Icelandic lakes

Abstract

Abstract:The distribution patterns of surface sediment diatom assemblages from 49 lakes were used to explore the relationship between limnological variables and diatom assemblages as well as to assess an ecological classifi cation system as a tool for the management and conservation of Icelandic freshwaters. Lakes were limnologically diverse ranging from deep, oligotrophic, ionically dilute lakes, to shallow lakes with a wide range of nutrient and ionic contents. Physical conditions (depth, surface area, surface water temperature) and nutrient and ion concentrations differed signifi cantly among ecological lake categories (i.e., plateau, spring-fed, direct-runoff, valley, glacial, and coastal lakes) (ANOVA, p < 0.05). Diatom assemblages were taxonomically diverse (329 taxa) with strong representation of planktonic, benthic and periphytic forms. Small benthic Fragilaria sensu lato (19 species and varieties) were the most abundant with combined abundances > 20 % in all but 4 of the lakes, most likely due to the generally cold lake water conditions in this subarctic region. Variation in diatom distributions was best explained by the combination of mean depth (infl uencing littoral versus planktonic habitats), surface water temperature, specifi c conductivity, alkalinity, total organic carbon, total nitrogen and SiO 2 in a canonical correspondence analysis (CCA). However, these variables did not explain distribution patterns amongst small benthic Fragilaria taxa, although some weak relationships between some taxa and these variables were evident. Distinct diatom assemblages and limnological properties among ecological lake categories support the classifi cation of Icelandic freshwaters based on major topographic, geological and hydrological characteristics. More detailed inclusion of lake depth along with lake basin form, as well as more refi ned categories of lake water origin and topographical positioning to better approximate regional climatic conditions, may improve the ecological classifi cation of Icelandic freshwaters for conservation and management practices.

Global warming triggers the loss of a key Arctic refugium

“…These gradual diatom trends are more difficult to interpret because the earlier diatom assemblages were dominated by several species and varieties of small benthic fragilarioid taxa, and early changes in PCA axes scores reflect subtle fluctuations among these taxa. Deciphering meaningful ecological differences among this group of fragilarioid taxa has always been a challenge [45][46][47], making palaeolimnological inferences based on changes among these taxa difficult. In the absence of additional monitoring data or regional stressor information in this remote region, we cannot draw definitive conclusions as to the underlying mechanism for these subtle fluctuations among benthic diatoms, but they probably reflect catchment-scale disturbances or natural variability.…”

On the geographical distribution and ecology of Pseudostaurosira cataractarum (Bacillariophyceae): new findings in the Palearctic and Neotropic ecozones

“…Several researchers have considered that these taxa are generalists with an r-strategy and their rapid substrate colonization and high reproduction rate confer them resilience to short-term environmental fluctuations, making them very competitive species under unstable limnological conditions (Lotter and Bigler 2000;Weckström and Juggins 2006;Lotter et al 2010). The presence of a given genus and species of this group has been used as an indication of changes in prolonged ice cover, water temperature, nutrient status, salinity, pH and climatedriven environmental variables (Smol 1988;Dixit et al 1992;Wilson et al 1997;Douglas and Smol 1999;Lotter and Bigler 2000;Karst-Riddoch et al 2009). Thus, they are regarded as good environmental indicators in research projects focused on paleo-and neolimnological conditions.…”

Interactions between climate and landscape drive Holocene ecological change in a High Arctic lake on Somerset Island, Nunavut, Canada

“…Autecological studies in the Canadian Arctic Archipelago have determined habitat preferences of individual diatom species based on their distribution and abundances in different habitats (e.g., Bouchard et al 2004;Cremer et al 2005;Karst-Riddoch et al 2009). Planktonic diatoms, in Arctic lakes Cyclotella sensu lato, often increase in both relative and absolute abundances in response to availability of open water habitat during warm climate intervals (Douglas and Smol 1999;Rühland et al 2008;Devlin and Finkelstein 2011).…”